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Chapter 3 Cells & Their Functions

Chapter 3 Cells & Their Functions. The Role of Cells. Basic unit of all life Cytology – the study of cells Simplest structure that shows all the characteristics of life such as Organization Metabolism Responsiveness Homeostasis Growth Reproduction. The Role of Cells.

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Chapter 3 Cells & Their Functions

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  1. Chapter 3Cells & Their Functions

  2. The Role of Cells • Basic unit of all life • Cytology – the study of cells • Simplest structure that shows all the characteristics of life such as • Organization • Metabolism • Responsiveness • Homeostasis • Growth • Reproduction

  3. The Role of Cells • It is possible for a single cell to live independently of other cells • Protozoa • bacteria • Cells make up all tissues • All activities of the human body result from the activities of individual cells

  4. Microscopes • Stains – dyes that color cells and tissues to aid viewing • Compoundlight microscope • Magnifies 1000 times • 2 lenses • Uses visible light for illumination • Transmission electron microscope • 1,000,000 times magnification • Uses electron beam instead of light • Scanning electron microscope • 100,000 times magnification • Shows surface features, but in 3D view

  5. Cell Structure • All cells share certain characteristics. • Main parts: • Plasma membrane • Nucleus • Cytoplasm • Organelles

  6. Plasma Membrane • Formerly called the cell membrane • Function • Encloses the cell • Participates in growth & reproduction • Involved in cellular interactions • Regulates what enters and leaves the cell

  7. Plasma Membrane • Bilayer structure • Phospholipids • Cholesterol • Carbohydrates • Proteins • Channels • Transporters • Receptors • Enzymes • Linkers • Cell identity markers

  8. Plasma Membrane Proteins • Channels pores that allow specific ions to enter or leave • Transporters shuttle substances across the membrane • Receptors act as points of attachment for materials that act on the cell • Enzymes participate in reactions occurring at the plasma membrane • Linkers give structure to the membrane and help cells attach to each other • Cell identity markers are proteins that are unique to an individual’s cells. Important in immunity & tissue transplants

  9. Cell Nucleus • Nucleus is the biggest organelle in the cell • Organelles – specialized structures that perform different tasks for the cells • Control center of the cell • Contains chromosomes which govern all cellular activities • Nucleolus contains RNA, DNA, and proteins and manufactures ribosomes in the cytoplasm • Almost all DNA is found in the cell nucleus

  10. The Cytoplasm Cytosol – liquid part of cytoplasm containing nutrients and organelles such as: • Endoplasmic reticulum • Ribosomes • Mitochondria • Golgi apparatus • Lysosomes • Peroxisomes • Vesicles • Centrioles

  11. Endoplasmic reticulum Network of membranes that is either smooth or rough • Smooth ER – involved in lipid synthesis • Rough ER – comes from ribosomes attached to the ER • Ribosomes – necessary for protein synthesis and are either attached to ER or floating free

  12. Cell Organelles Cont. • Mitochondria – converts nutrients into ATP, the power plant of the cell. Active cells have more mitochondria than other cells • Golgi Apparatus – involved in sorting and modifying proteins and then packaging them for export from the cell • Centrioles - near the nucleus; help to organize the cell and divide the cell contents during the process of cell division

  13. Cell Organelles Cont. • Lysosomes – remove waste and foreign materials from the cells • Peroxisomes – destroy byproducts of metabolism • Vesicles – storage units of the cell, can also move materials into and out of cells

  14. Surface Organelles • Cilia – small hair-like projections that wave, creating movement of fluids around the cell. Respiratory passage cells have cilia and cells in the female reproductive tract. • Flagellum – long whip-like extension for movement. The only cells in humans with flagella are sperm cells.

  15. Cellular Diversity • Size • Average size is 10-15 micrometers • RBCs are small – 7 micrometers • Muscle cells are big – 200 micrometers • Composition – most human cells have all the organelles. Some cells have more than one type of organelles than another due to their function

  16. Protein Synthesis: Chromosomes & Genes • Chromosomes are the hereditary units that govern cells • 23 pair, 46 total • Divided into genes • Genes carry the messages for the development of particular inherited characteristics and do so by directing the manufacture of proteins in the cell.

  17. DNA & RNA • Genes are made of DNA – deoxyribonucleic acid • DNA is composed of nucleotides • RNA – Ribonucleic acid – a related compound which participates in protein synthesis but is not part of chromosomes • RNA is composed of nucleotides

  18. DNA & RNA Composition • DNA is composed of • 4 nucleotides • Adenine (A) • Guanine (G) • Cytosine (C) • Thymine (T) • RNA is composed of • 4 nucleotides • Adenine (A) • Guanine (G) • Cytosine (C) • Uracil (U)

  19. NucleotideStructure • Composed of three units • Sugar – • RNA – ribose • DNA - deoxyribose • Phosphate - an area containing phosphorus • Nitrogen base – an area containing nitrogen

  20. Deoxyribose & Ribose

  21. DNA Structure • DNA is built like a ladder • Sugar-phosphate backbone • Nitrogen bases are the steps • 2 DNA strands make a pair • Nucleotide adenine always pairs with thymine • Guanine always pairs with cytosine • 2 DNA strands are bonded together with hydrogen bonds – form double helix

  22. RNA • RNA interprets the information from the DNA blueprint to synthesize proteins • RNA is found almost entirely in the cytoplasm • RNA is a single strand of nucleotides • There are 3 types of RNA • mRNA – messenger RNA • rRNA – ribosomal RNA • tRNA – transfer RNA

  23. The Role of RNA Protein synthesis • Transcription • Messenger RNA (mRNA) • Translation • Transfer RNA (tRNA) • Ribosomal RNA (rRNA)

  24. Protein Synthesis and RNA • DNA breaks its bonds and uncoil into single strand • Transcription – transfer of information from DNA to mRNA in the nucleus >> matching RNA strand forms based on pairing • mRNA leaves the nucleus and travels to a ribosome in the cytoplasm

  25. Transcription.

  26. Translation.

  27. Cell Division • Meiosis • Sex cells • Mitosis • Somatic cells

  28. Cell Division - Mitosis • Mitosis – the process of cell division where an original parent cell becomes two identical daughter cells • Before mitosis can occur, DNA must double – therefore, the 46 chromosomes in the nucleus must double

  29. Interphase • The stage of life in a cell between one mitosis and the next • During this phase, DNA uncoils and each strand takes on a matching strand of nucleotides to make up 2 new DNA strands, each one identical to the original and each other • The new, uncoiled DNA strands are held in the centromere until mitosis • A typical cell spends most of its cycle in interphase and a relatively short time in mitosis

  30. Mitosis • 4 stages • Prophase • Metaphase • Anaphase • Telophase

  31. Mitosis - Prophase • The new double strands of DNA coil tightly into a double helix • The nucleolus and the nuclear membrane begin to disappear • All other organelles disappear except those needed for mitosis • Two centrioles in the cytoplasm move towards opposite ends of the cell • Thin spindle fibers begin to form between the centrioles

  32. Mitosis - Metaphase Chromosomes attach to spindle fibers and line up across the center of the cell

  33. Mitosis - Anaphase The centromere splits and the duplicated chromosomes separate and begin to move towards opposite ends of the cell

  34. Mitosis - Telophase • A membrane appears around each group of separated chromosomes, forming 2 new nuclei • The plasma membrane pinches off to divide the cell

  35. Mitosis : Summary • At the end of mitosis there 2 new cells • Each daughter cell has exactly the same DNA as the original • All organelles reappear in the daughter cells

  36. Movement of Substances Across the Plasma Membrane Travel across the membrane is based on several factors: • Molecular size • Solubility • Electrical charge

  37. Movement That Does Not Require Cellular Energy Passive transport • Diffusion • Osmosis • Filtration • Facilitated diffusion

  38. Diffusion • Concentration gradient - constant movement of particles from a region of higher concentration to one of lower concentration • Equilibrium - diffusing substances spread throughout available space until their concentration is equal everywhere • Passage is limited to those particles small enough to pass through spaces between molecules of the plasma membrane

  39. Osmosis • The diffusion of water through a semi-permeable membrane • Water moves from an area where there is more water molecules to an area where there is less water molecules • The solvent water moves from an area of lower solute concentration to an area of higher solute concentration • Water follows salt

  40. Osmotic Pressure • Describes the tendency of a solution to draw water into it • Directly related to concentration: the higher the concentration of a solution, the greater the tendency to draw water in • A measure of the force driving osmosis • Determined by applying enough pressure to the surface of a liquid to stop the flow of water by osmosis

  41. Filtration • Passage of water containing dissolved materials through a membrane as a result of a “pushing” force on one side • Movement of materials out of the capillaries and into the tissues under the force of blood pressure • Movement of materials out of the blood and into urine in the kidneys

  42. Facilitated Diffusion • Movement of materials across the plasma membrane in the direction of the concentration gradient but using transporters to move the material at a faster rate • Glucose

  43. Movement That Requires Cellular Energy Active transport • Bulk transport or vesicular transport • Endocytosis • Phagocytosis • Pinocytosis • Exocytosis

  44. Active Transport • Moves solute particles in or out of the cell opposite of the direction they would normally flow by diffusion • Transporters – proteins in the plasma membrane that are required to transport the particles • Nerve and muscle cells depend on active transport of Na, K and Ca for proper function

  45. Endocytosis – bulk transport of large quantities of materials into or out of the cells • Phagocytosis – large particles are engulfed by the plasma membrane and moved into the cell • White blood cells rid the body of foreign materials • Pinocytosis – cell membrane engulfs droplets of fluid

  46. How Osmosis Affects Cells • Isotonic – solutions with concentrations equal to the concentration of the cytoplasm • Blood plasma, interstitial fluid, normal saline (0.9% salt), 5% dextrose • Hypotonic – a solution less concentrated than intracellular fluid • A cell in hypotonic solution will draw water in and may burst • Hemolysis – a red blood cell drawing too much water in and bursting • Hypertonic – a solution more concentrated than intracellular fluid • Crenation – the process by which a cell that loses water to surrounding fluids and shrinks

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